Keep the product hydrated. It does not like Sunlight, heat, humidity etc... So you want to keep the product moist and not let it dry out. If the product dries out it will stop working. One method of doing this is by applying late in the evening and removing early in the morning. Or you could cover the product with paper bags, plastic wrap etc... to keep the moisture locked in. The product was designed for spray use so this will always be the best application. If you must brush (which is not recommended) it requires a certain "build" to work properly. In this instance you will need to apply the product "thickly" (not "thinly" like painting a wall). I find the magic time to be about 6 to 8 hours, although many customers report that 4 hours seems to work well. The bottom line is that if the product is moist (and not dried out) it can continue to work but once it has dried then you might as well remove it because it will not be doing anything further. Always try a small test area first to get a good understanding of how the product works and its overall effectiveness in your situation/environment.